- Geotechnical assessment of port facility for offshore wind storage, assembly, and deployment
- Geotechnical desktop study
- Environmental Site Assessment
- Geotechnical investigation and bearing capacity evaluation of crane loading and component storage
- On-land and underwater survey of 100-year-old granite seawall
- Stability analysis of crane loading on granite seawall
- Foundation design for tower assembly and storage structures
Challenge
While staging offshore wind operations for Block Island Wind Farm, the developer was confronted with an aging port facility where the bearing capacity of the facility and condition of the quay was largely unknown. GZA was retained by Deepwater Wind and General Electric to conduct a geotechnical assessment of the facility where proposed staging operations would create larger loadings than previously encountered.
Solution
GZA conducted a geotechnical desktop study of existing geotechnical information and data on the century-old granite seawall to provide bearing capacity recommendations for storage and transport of the wind farm components. GZA also conducted a Phase I Environmental Site Assessment; a subsurface geotechnical investigation to fill data gaps; and a top side, above water, and underwater survey of the seawall. A stability analysis of the seawall used anticipated crane loading for transfer and loadout of the tower segments.
GZA recommended a crane offset of the seawall due to the high crane loading and designed a crane pad. A soil information package evaluated the soil conditions in front of the berth during load out of components for stability of the jack-up vessel used for the loadout. GZA designed the foundations for temporary structures used to assemble and store the tower segments. The tower segments—approximately 90’ tall, 60,000 pounds, and designed for wind loading of over 100 mph—were stored upright and fit with electrical components. The storage frame foundations were designed so that a self-propelled modular transporter (SMPT) could be driven under the frame to transport the tower. GZA’s design calculations and drawings were reviewed and approved by the project Verification Agency, ABS Consulting. During construction of the temporary foundations, GZA provided construction observation and conducted concrete and grout testing.
Benefit
GZA’s geotechnical and environmental assessments and foundation design provided the critical information the developer needed to proceed, confident that the facility was able to accommodate the extreme crane loadings and provide support for construction of the offshore wind farm.